1. Field of the Invention
The present invention is directed to ultrasonic pipe inspection systems and methods.
2. Description of Related Art
Many systems have been developed to inspect pipe. A variety of these systems measure the diameter, ovality, and wall thickness. They also look for flaws in the pipe such as cracks and pits. Some versions of these systems have been adapted for inspecting coiled tubing (CT). These systems can be categorized in three major types: nuclearxe2x80x94some type of radiation such as gamma rays are passed through the pipe and the reflections are measured; electromagneticxe2x80x94magnetic flux is passed through the pipe and the flux flow or flux leakage is measured; and ultrasonic (UT)xe2x80x94ultrasonic sound is passed through the pipe and the reflections are measured. Nuclear measurements require a nuclear source, which makes them impractical for many applications.
Systems using electromagnetic measurements have been used for diameter and ovality measurement, and for finding anomalies, flaws and defects in the pipe, such as cracks, but often such systems have not proven accurate for measuring the wall thickness in one localized area of the pipe. As and example, an electromagnetic inspection system for CT is discussed in U.S. Pat. No. 5,914,596. UT inspection systems have been used for measuring the localized wall thickness of a tubular. They are also capable of An exemplary UT system for inspecting CT is shown in U.S. Pat. No. 5,303,592.
Wall thickness measurement is often important when inspecting CT. Some services, such as CT fracturing, tend to erode the inner surface of the CT in some areas. Also, the CT wall may be worn when used in wells with chrome tubulars. Thus, UT inspection is desirable as a method of locating CT dimensional variations, flaws, defects, and/or anomalies.
With UT inspection systems an ultrasonic probe or probes are acoustically xe2x80x9ccoupledxe2x80x9d with the pipe. A UT probe contains both the UT transmitter and the UT receiver, which may or may not be the same device. Alternatively one probe may contain the transmitter and a different probe may contain the receiver. xe2x80x9cProbexe2x80x9d refers to all types of UT devices used to make UT measurements and can include, but is not limited to, systems that use a spacer in front of a probe, the spacer sometimes referred to as a xe2x80x9cdelay linexe2x80x9d which modifies the acoustic response of the system and protects the probe. The probe is in contact with a coupling medium which is in contact with the pipe. The UT sound waves pass from the probe, through the coupling medium and into the pipe. Often a liquid, such as water, is used as a coupling medium, as in U.S. Pat. No. 5,303,592. A circulating system is often used to circulate the coupling fluid and keep it clean. Seals are used to prevent the coupling fluid from escaping around the pipe. Often the coupling fluid treatment and sealing system makes UT systems such as the one described in U.S. Pat. No. 5,303,592 difficult to use in some applications.
In one prior art effort to avoid problems with coupling fluid systems, a UT probe is inserted inside of a wheel which rolls along the pipe. An example of such a system is shown in U.S. Pat. No. 4,202,216. The UT probe presses against the inside surface of a tire. The outside surface of the tire is pressed against the pipe. Alternatively the inside of the tire is filled with a coupling fluid which serves as a coupling medium between the probe and the inside surface of the tire. These wheel-probe based UT systems may be too complex for some pipe inspection applications. Alternatively the probes and coupling fluid may be in a cushion or pad which is placed against the pipe. Usually an additional coupling fluid must be sprayed on the pipe to provide good coupling between the pad and the pipe. These wheel probes use a solid tire made of a material through which the sound waves will pass, such as polyurethane or a rubber compound.
Many efforts have been made to mark CT in some way so that reference points along a CT string can be easily located. Magnetic markings, paint markings, and surface etching are some of the attempted methods. Such reference points are used to verify a depth or length measurement or to determine a location along a string.
There is a need for a UT pipe inspection system which does not require a complicated coupling fluid system and can be used easily in oilfield service, pipeline and pipe manufacturing environments. There is a need for an accurate and efficient method for providing easily sensed or recognized markings on a tubular member used in wellbore operations.
In certain embodiments, the present invention discloses methods for ultrasonically inspecting pipe, the pipe having a longitudinal axis, the method including compressing an elastomeric element with a compressing force from a piston or other compressing member, the elastomeric element between an ultrasonic probe (or probes) of an ultrasonic pipe inspection system and a pipe to be inspected, the compressing force forcing the elastomeric element generally radially against the pipe and/or forcing the elastomeric element against the probe(s), and the compressing force in the general direction of the longitudinal axis of the pipe, at an angle to the pipe, or, on one particular aspect, normal thereto. In other aspects the compressing member and its associated structures and mechanisms are deleted, but a packer element is used as the elastomeric member which is positioned in a housing with one or more ultrasonic probes within the housing, within the elastomeric member, or affixed to and outside of the housing.
The present invention, in certain embodiments, discloses a method for performing UT pipe inspection using a packer element as the primary coupling medium between the UT probe and the pipe. A packer element is typically used to seal around a pipe, separating the fluids in a well from the atmosphere. In certain aspects when the tubular string is CT, a stripper packer is used. U.S. Pat. No. 5,566,753 shows two types of CT stripper packers which are common. In the case of drilling with jointed pipe a stripper packer (U.S. Pat. No. 4,486,025) and/or an annular BOP and/or rotating BOP contains the packer element(s). In the case of hydraulic work-over (often known as xe2x80x9csnubbingxe2x80x9d) operations, several types of sealing mechanisms containing packer elements may be used, including stripper bowls and annular BOPS, as are discussed in U.S. Pat. No. 5,988,274. Stripper packer apparatuses useful with systems according to the present invention include, but ar not limited to, those with pistons or rams that apply force either generally radially (at a right angle to the pipe) or generally in the direction of the longitudinal axis of the pipe.
In certain aspects the elastomeric or packing elements in systems and methods according to the present invention are made of an elastomeric material such as, but not limited to, a rubber compound, polypropylene, polytetrafluoroethylene, polyvinylchloride, plastisols, and viton (tm) material. The elements may be composed of a single piece made of one or more elastomeric material(s), or may be composed of multiple pieces made of one or more elastomeric materials. Many methods can be used to compress the packing element against the pipe to form a pressure seal. Techniques according to the present invention for inspecting pipe through an elastomeric element may be used in any of the aforementioned devices. These techniques may also, according to the present invention, be used in a device with an elastomeric element and compression apparatus built for performing pipe inspection which may or may not also serve as a pressure barrier.
In certain aspects according to this invention, an element is compressed between UT probe(s) and the wall of the pipe, to form the primary coupling media. A thin film of a fluid may or may not be placed between the probe(s) and the element, and/or between the element and the pipe to enhance the acoustic coupling. The probe(s) are then used to inspect the pipe using known UT inspection techniques and signal generation and processing systems.
In certain aspects, to enhance the elastomeric material""s ability to transmit acoustic waves, multiple elastomeric materials are used. For example, and not by way of limitation, the material between the UT probe(s) and the pipe may be selected for its ability to transmit acoustic waves, while the remaining material may be selected for its ability to form a pressure seal. The UT probe(s) or a portion of them may be embedded in the element, affixed to it, or screwed into it. In certain embodiments, the acoustic material does not go all the way through the elastomeric element and does not contact the pipe to prevent wearing of the acoustic material by contact with the pipe; e.g., in one particular embodiment there is about one half inch of elastomeric material between the acoustic material and the pipe.
In certain embodiments systems according to the present invention to use one or a plurality of areas or rings of increased or decreased wall thickness on pipe, tubulars or coiled tubing. It is within the scope of this invention to position one or more of such areas at known locations so that, upon sensing of the presence of the area(s), the amount of pipe, etc. and/or the location of an item thereon can be accurately calculated and/or displayed. For example, positioning an area of increased wall thickness with a known wall thickness that acts as a sensible signature for that area a thousand feet above the end of coiled tubing makes it possible for an operator to know when a thousand feet of the coiled tubing has been inserted into a wellbore and, in retrieving the coiled tubing from the wellbore, to know when there is still a thousand feet left in the wellbore to be retrieved. Positioning an area of known increased or decreased wall thickness at a known distance from an apparatus or device on a tubular string permits accurate locating of the device within the wellbore and/or provides an accurate indication of the location. Similarly, the depth of a wellbore and/or the depth at which is located the the end of tubular string can be determined by using one or more areas of known sensible and/or unique wall thickness at known locations on a tubular string. In one aspect, a sensible area of known and/or unique wall thickness near the end of coiled tubing provides an indication to an operator that the end of the tubing is near as it is being withdrawn from a wellbore so that appropriate action can be taken, e.g., slowing down of the rate of tubing retrieval to prevent damage to equipment. In other embodiments as series is used on a pipe, etc., of spaced-apart areas or rings of a wall thickness that differs from the areas on either side of the series and such areas or rings can be of the same or of different wall thicknesses themselves. In one aspect simply the number of areas or rings of different wall thickness is used to provide a locating structure.
The present invention recognizes and addresses the previously mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one skilled in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.